Service Limits Check Questions
Reserved Instance Optimization Check Questions
For more information about Trusted Advisor, see the Trusted Advisor section of the AWS Support FAQs.
Q. What service limits do you check?
The following table shows the limits that Trusted Advisor checks.
| Service |
Limits |
|---|---|
| Amazon Elastic Compute Cloud (Amazon EC2) |
Elastic IP addresses (EIPs) Reserved Instances - purchase limit (monthly) |
| Amazon Elastic Block Store (Amazon EBS) |
Active volumes Active snapshots Provisioned IOPS Provisioned IOPS (SSD) volume storage (GiB) General Purpose (SSD) volume storage (GiB) Magnetic volume storage (GiB) |
| Amazon Relational Database Service (Amazon RDS) |
DB instances DB parameter groups DB security groups DB snapshots per user Max auths per security group Read replicas per master Storage quota (GiB) |
| Amazon Simple Email Service (Amazon SES) |
Daily sending quota |
| Amazon Virtual Private Cloud (Amazon VPC) |
Elastic IP addresses (EIPs) Internet gateways VPCs |
| Auto Scaling |
Auto Scaling groups Launch configurations |
| Elastic Load Balancing (ELB) |
Active load balancers |
We are constantly working on including more services in this check. Your feedback is really helpful to us.
Q. What are the default service limits?
For a list of the default service limits and instructions for requesting increases, see AWS Service Limits.
Q. How can I get the Service Limit data with command-line tools?
This AWS Command Line Interface command displays all of the resources in your account that Trusted Advisor has flagged as approaching or reaching the limit, sorted by limit name.
aws support describe-trusted-advisor-check-result --language en --check-id eW7HH0l7J9 --query "result.sort_by(flaggedResources[?status!=`ok`],&metadata[2])[].metadata" --output table
Here is sample output from the command. The fourth column shows the limit amount, and the fifth column shows the current usage.
The filtering and sorting in the --query option requires AWS CLI version 1.3.0 or later.
To display all resources, replace [?status!=`ok`] with [ ]. To sort by a different column, change the number in &metadata[2]. For example, to sort by region, use &metadata[0].
-----------------------------------------------------------------------------
| DescribeTrustedAdvisorCheckResult |
+-----------+------+-----------------------------------+----+----+----------+
| us-east-1| ELB | Active Load Balancers | 20 | 18 | Yellow |
| us-east-1| EC2 | Elastic IP addresses (EIPs) | 5 | 5 | Yellow |
| us-west-1| EC2 | Elastic IP addresses (EIPs) | 5 | 4 | Yellow |
| us-east-1| EC2 | VPC Elastic IP addresses (EIPs) | 5 | 4 | Yellow |
| us-west-2| EC2 | VPC Elastic IP addresses (EIPs) | 5 | 5 | Yellow |
+-----------+------+-----------------------------------+----+----+----------+
Q. What data set are you using to make a Reserved Instance recommendation?
We calculate the recommendation based on the usage in the last completed calendar month. For example, if it is the 25th of April, the recommendation is based on data from March 1 to March 31.
Q. Does the recommendation consider volume discounts?
No, the recommendation uses standard pricing. Actual results may vary on discounted pricing tiers. We recommend contacting your sales representative by completing the AWS Sales & Business Development form to review a more detailed optimization plan if you are receiving volume discounts.
Q. I just purchased a new Reserved Instance. Why isn’t it showing up in the recommendation?
New Reserved Instance purchases are updated on a daily basis. Refresh the check 24 hours after you make your purchase to see the new recommendation.
Q. How do you calculate the optimized number of Reserved Instances?
Our system analyzes the hourly usage history during the previous calendar month across all consolidated accounts. The system calculates the number of running instances in each availability zone and for each type of instance. An hourly cost is determined by aggregating the cost of all instances that ran the previous month, whether they ran as on-demand or as a Reserved Instance. In addition to the hourly usage charges, the system calculates a fixed charge by amortizing the one-time upfront fees for each Reserved Instance already purchased.
By adding the aggregated hourly charges and the amortized upfront fees, the system is able to determine your baseline cost for the month. The system then incorporates the hourly and amortized upfront costs for additional Partial Upfront Reserved Instances, and the amortized upfront costs of any existing Reserved Instances into the calculation. Given the baseline cost based on the previous usage, and the costs for adding additional Partial Upfront Reserved Instances, the system uses a simple gradient descent algorithm to determine the number of Partial Upfront Reserved Instances that would result in the lowest overall cost.
Q. How do you amortize the cost of existing Reserved Instances?
The upfront fee for each Reserved Instance is amortized over the period of the Reserved Instance. In simple terms, if the upfront fee was $1200, and the term length was one year, the system will divide $1200 by 12 months, resulting in a cost of $100 per month.
Q. I have many accounts, and the availability zones are different for each one. How do you account for that?
We normalize all availability zones across all consolidated billing accounts and reflects the values using the primary payer account mapping.
Q. Do you include other Reserved Instance types in the recommendation?
Only Partial Upfront Reserved Instances are recommended by this check. However, hourly usage charges and amortized upfront fees for other Reserved Instance types are included in the calculation.
Q. Why are there separate sections for 1-year and 3-year Reserved Instances?
Customers have a choice between buying 1-year and 3-year term Reserved Instances. This check assumes you will purchase Reserved Instances for either 1-year or 3-year terms, not both. As a result, recommendations for purchasing additional 1-year or 3-year term Reserved Instances are not additive across both term lengths, so recommendations are called out separately. To illustrate: in a recommendation for 3 additional 1-year Reserved Instances or 4 additional 3-year Reserved Instances, we are recommending the purchase of 3 or 4 Reserved Instances respectively, not a total of 7 additional Reserved Instances.
Q. Are all instance types of instances included in the recommendation?
Recommendations are available for Linux/UNIX and Windows Reserved Instances. The calculation excludes usage and recommendations for Red Hat Enterprise Linux, SUSE Linux Enterprise, Amazon RDS, and Amazon ElastiCache.
Q. I use spot instances. Do you include spot rates in the calculation?
Due to the variability of the spot instance market, the system uses on-demand rates when calculating the optimized number of Reserved Instances.
Q. Does the recommendation include any money I make if I sell my existing Reserved Instances to purchase the recommended Partial Upfront Reserved Instances?
The system does not include any money that could result from the sale of existing Reserved Instances when calculating the optimal number of Partial Upfront Reserved Instances.
